This invention came about as a result of public utilities' need to know the characteristics of the contents of pipelines which may be excavated by repair crews.
Various techniques have been used by public utilities to provide later identification of specific pipe systems after they are installed and buried. The problem is, nature is not particularly cooperative in maintaining the schemes of identification originated by man.
Survey crews and draftsmen are often quite specific in preparing crossing locations for buried conduits and they are more than adequately related to landmarks available at the time the pipe is buried. Unfortunately, the street curbline may be changed by the city, the centerline of the street may be changed by the government entity responsible for maintenance, the alignment of power lines between power poles may be shifted, other pipelines or electrical conduits may be buried above or below the critical pipeline or installed at an angle crossing the same.
The problem created is one to be solved by an excavation crew on-site. It is critical for the safety of working crews and citizens near the site of an excavation for the operating crew to know the characteristics of the contents of pipelines.
For example, an excavation crew from a natural gas public utility working in an urban area will believe that it knows about where a particular pipeline is located. This information will be based on data collected from the engineering department of the utility in question. The problem is that the on-site excavation crew may find the wrong pipe and not know it. The potential for disaster is self-evident if the crew thinks that the excavated pipe is a water pipe and it turns out to be a natural gas transmission line operating at 150 psi and flowing at 25 ft/sec.
There is a need in the utility industry for an apparatus and procedure for determining physical characteristics of the fluid inside a pipeline without breaching the sidewall of the pipe. Such data would ensure that the excavation crew is operating on the right pipeline and in addition will take the necessary precautions for safety of the population when the pressure flow rate and direction of flow are available prior to the time the intended structural modifications are made to the pipeline.